Greetings, I've attempted to use DTAF as a trophic tracer for two
ciliates (Oxytricha fallax and Trithigmostoma cucullulus) and found that
the ciliates could discriminate between DTAF-stained and unstained
diatom algal cells. They cilIAtes avoided the DTAF stained cells when
presented with a 1:1 mix of stained and unstained cells. In fact, I
tried several stains, all of which were toxic to the ciliates. I ended
up 14-C labelling the diatoms and following uptake. This is a problem
for those people that wish to use 14-C with bacterial feeders. It is
nearly impossible to separate the bacteria from the protozoa to
accurately measure uptake. The ciliates were easy, as they are large
and can be picked individually from the feeding arena and washed in
particle-free water to minimize carry-over of 14-C labelled algae. I
don't know if this is of any help, but it may be of some interest.
Good Luck, Joe Balczon
Graduate Program in Ecology
Penn State University